The present invention relates to an adhesive composition, in particular to an adhesive composition for bonding a lining tube on the internal surface of an existing old pipe such as an existing gas pipe, water pipe, etc. so as to repair the same.
People have found that if an existing old pipe is treated by bonding a flexible lining tube to the internal surface thereof, such a treated existing old pipe will have a sufficient air-tight property and will be very strong in preventing pipeline leakage and/or earthquake damage.
For example, there has been known a method of repairing an existing underground gas pipe by reversing a flexible lining tube into the pipe without trenching on road surface along the pipe. According to such a method, at first, a belt is introduced into an existing pipe so that one part of the belt is extending through the pipe over the entire length thereof. Then, another part of the belt is introduced into a flexible lining tube so that this part of the belt is extending through the lining tube along the entire length thereof. Afterwards, a necessary amount of adhesive agent is sealed into the lining tube, and one end of the lining tube is reversed to be fixed at one open end of the existing pipe. Subsequently, a pressurized fluid is applied from behind to continuously cause the reversal of the lining tube in the existing pipe, so that the lining tube may be introduced into the pipe and the reversed lining tube may be bonded on to the internal surface thereof. Such reversal and introduction of the lining tube into the existing pipe can be effectively directed by pulling the above belt introduced in advance into the existing pipe. In this way, the lining tube reversed in the existing pipe can adhere to the pipe internal surface by virtue of the adhesive agent and the pressurized fluid being applied from behind.
The lining tube adhered to the internal surface of the existing pipe is usually made of a flexible gas-impermeable material, therefore it is effective in repairing any corrosion holes and is also effective in preventing any possible damages caused due to an earthquake or the like. However, since the above method involves too many preparation steps before the operation of reversing and introducing a lining tube into an existing pipe, a time period required in the whole pipe repairing process is relatively long and hence the cost for repairing an existing pipe is comparatively high.
In order to overcome the above problem, Japanese Patent Publication 61-20411 has suggested an improved method as shown in FIG. 3. In the process of FIG. 3, at first, a leading block c is introduced into an existing pipe a through an open end b thereof, then an adhesive agent d is introduced into the existing pipe a. Subsequently, one end of a lining tube e is reversed to be fixed at the open end b of the existing pipe a. Afterwards, a pressurized fluid is applied from behind, as shown by an arrow g to continuously cause the reversal of the lining tube e, so that the lining tube e may be introduced into the existing pipe a. At the same time, the leading block c is pulled forward by a towing wire f, facilitating the forward movement of the adhesive agent d and reversing movement of the lining tube e. In this way, the lining tube e can adhere to the internal surface of the existing pipe a by means of the adhesive agent d and pressurized fluid g being applied from behind.
In the process shown in FIG. 3, the leading block c is used to prevent the adhesive agent d from moving too fast to ensure that the internal surface of the existing pipe a may be exactly coated with the adhesive agent d.
Although a process of FIG. 3 is allowed to dispense with some preparation steps before the operation of reversing a lining tube into an existing pipe, there is still a problem which can be concluded as follows.
Firstly, since the adhesive agent used in the process shown in FIG. 3 is usually an epoxy resin which has been found to have a relatively great friction resistance between pipe internal wall and the lining tube e, it is often difficult for the lining tube e to be smoothly reversed and moved forward through the pipe a over the entire length thereof. For this reason, in each such a process, the leading block c is required to be pulled forward by a towing wire f. Thus, it is necessary for the wire f to be in advance introduced into the existing pipe over the entire length thereof, and a towing apparatus is needed to pull the wire f to cause the leading block c to move forward. As a result, more equipment is needed and the whole repairing process becomes complicated.
Secondly, because the adhesive agent used in the process shown in FIG. 3 is usually an epoxy resin which has been found to have a relatively great friction resistance between pipe internal wall and the lining tube e, it is often difficult for the lining tube e to be smoothly reversed and moved forward through the pipe a, especially when the lining tube e arrives at a bent portion of the pipe. As a result, the lining tube e will get stuck and become unmovable at the bent portion of the existing pipe, causing the whole repairing operation to be undesirably stopped.
In fact, during the process shown in FIG. 3, if the leading block c is not pulled forward by a towing wire f which requires a towing apparatus, then a further stronger and more energetic pressurized fluid g is required to be applied from behind, thus requiring a pressurizing equipment of further larger scale.